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USAF Fund B-52 Engine Replacement

Does this mean that the E3 (TF33) engines will also become unsupportable?

The answer is a bit more complex than that, but in a nutshell, yes. However in the case of AWACS there is an existing thoroughly tested, in production solution: CFM engines. The B-52 does not have that option and the solution is not only not yet developed, but the engine swap is more complicated. And much much more complicated than the engine swap itself is the possible impact on the B-52's weapons release envelopes caused by an engine swap, which AWACS does not have to contend with. That's why it's being addressed now on the B-52, many years before the actual need. Further, since an engine swap MUST be done on the B-52, the earlier it is done the more money will be saved AFTER the swap, potentially paying for itself in savings.

And FWIW, the most difficult part of an engine swap on AWACS will be deciding to go with the older standard CFM-56 engines, or the LEAP versions which cost more, but are more efficient. Are the savings worth the expense when the airframes may not have that many more years left in them? Or do the AWACS users commit early to a life extension program so that the potential savings can be realized?

“A new US Air Force document released last week outlines the details, timeline and likely competitors for a plan to acquire at least 608 new turbofan engines to replace the eight Pratt & Whitney TF33s on each of 76 Boeing B-52H bombers in the US Air Force fleet........

The new engines must not alter the aircraft’s take-off performance and the weapon release envelope, the document says.“.....

I saw a photo of a B52 in flight with 4 engines. Can't remember the make I'm afraid. Was the early 80's I think.

Bobby, there have been several proposals to put 4 engines on the B-52 over the decades, but that has now been shelved. Two B-52F's were used to test a single large fan (in place of an inner engine pair) for the C-5 and 747 program, but I do not believe one ever flew with 4 large fans other than in artists renderings.

If all these TF-33's get freed up coming off B-52's and the remaining K/E-135's that still have them + spares, I do wonder if that would be enough to keep the smaller E-3 fleet running?

If I had to take a guess, the weapon-release issue would involve the airflow between the new and larger nacelle and the body side and its effects on the pylon and stores.

Everyone please remember that the B-52 does not carry weapons only internally. It has very large EXTERNAL weapons pylons that carry a VERY wide variety of weapons. Significantly altering the airflow under the wings would necessitate recertifying not just all those weapons, but also the very large variety of weapon combinations over multiple flight conditions. That is a HUGE deal potentially much more difficult and time consuming to test for than the engine swap. This was one of the drivers that drove the eight small engine solution vs the four large engine solution.

If all these TF-33's get freed up coming off B-52's and the remaining K/E-135's that still have them + spares, I do wonder if that would be enough to keep the smaller E-3 fleet running?

Maybe, but doubtful. The engines become unsupportable not because of a dearth of numbers, but because the materials and manufacturing methods required to produce the necessary parts simply become unavailable.

Talk to the hobbyists that try to keep steam locomotives running. Not only are the parts no longer available, no one knows how to build those parts anymore. Heck no one can even figure out how to build the F-1 engines that powered the Saturn V moon rockets and they are of more recent vintage than the TF-33. It's a lost art. The problem is even more acute when we're talking about electronics. A lot of the chips that power 10 or even just 5 year old avionics are no longer being made and there is no equipment around anymore to make them. Obsolescence is a HUGE deal and must be carefully planned for.

I saw a photo of a B52 in flight with 4 engines. Can't remember the make I'm afraid. Was the early 80's I think.

Nope, not a photo. Artist's rendering. Both the Rolls RB211 and the P&W2040 were considered as possibilities. Nothing came of the ideas, largely because the USAF was agin it. USAF was convinced that the B-52's days were numbered and they would be replaced by the B-70, then the B-1A, then the B-1B, then the B-2, and so on. They thought any money directed at the B-52 would be money competing with those shiny new bombers. But now that they've decided to retire both the B-1 and B-2 and keep the B-52 for multiple more decades, they're finally taking a serious look at re-engining because they have to. And once again, contrary to the various skeptics and cynics, this is a top down idea from USAF trying to solve a real problem, not a bottom up idea from engine manufacturers wishing to sell more engines.

This seems like excess money chasing spending opportunities to me. The US's large engagement in Afghanistan is supported via a 1000 mile truck based logistics chain maintained over less than spectacular Pakistani highways. The true cost per gallon of fuel there is surely several times the norm, yet no one complains. So I don't buy the idea that economics are a factor here either. The minimal usage of the B-52s, even lower than that of corporate jets, make any economic return on a multi billion re-engining deeply implausible. Meanwhile, to claim that parts for a 70 year old design cannot be efficiently made any more is just silly. Maybe they would not be made as badly as before, because metallurgy has progressed, but there is no conceivable reason that TF-33s could not be replicated today, at much lower cost than re-certifying the B-52 for a whole new propulsion system.

Etudiant, it's not that simple. Some of the manufacturing processes and alloys used 70 years ago have been effectively banned due to EPA and OSHA regulations. Newer processes and alloys result in parts that have different mass characteristics - which affects other parts in the engine - which in turn affect other parts, and pretty soon you need to remake the entire engine. So what you end up with is an very expensive re-development of a 70 year old engine design. All the costs of a new, modern engine with the crappy performance of the original. When we looked at the RB211-535 re-engine ~20 years ago, they were looking at a lease arrangement. The savings in fuel and engine maintenance alone would have paid the lease costs (and that was without factoring in the fact that aerial refueling fuel costs several times more than stuff uploaded on the ground. Plus, a ~30% reduction in fuel burn means a corresponding improvement in range and/or greater payload capabilities. HH - I doubt the USAF would ever go for a replacement 'bomb truck' - the Air Force brass want their new stuff to be fancy - they just can't help themselves. If they started out with a RFP for a new bomb truck, they'd add so much crap to it before they were done that it would end up costing more than a B-2 (I'm not even remotely optimistic that the new B-21 will come in at anything less than a $Billion per copy and will be less than 10 years late). George, you are correct that the CMF56-2 that was used to re-engine the KC-135 (and DC-8) is long OOP, but the CFM56-7 on the 737NG isn't going OOP anytime soon (and even when it does, figure it'll be in commercial service at least another 30 years). While I can see some major obstacles to using the LEAP on the P-3 (among other things, it's significantly heavier than the CFM), I don't think a re-engine with the CFM56-7 would be too much worse than the -2. Plus the -7 is already in the US inventory on the P-8. That being said, I suspect the USAF will spring for new AWACs aircraft rather than re-engine.

Bobby, there have been several proposals to put 4 engines on the B-52 over the decades, but that has now been shelved. Two B-52F's were used to test a single large fan (in place of an inner engine pair) for the C-5 and 747 program, but I do not believe one ever flew with 4 large fans other than in artists renderings.

If all these TF-33's get freed up coming off B-52's and the remaining K/E-135's that still have them + spares, I do wonder if that would be enough to keep the smaller E-3 fleet running?

The current trend is to replace such platforms with large business jets with satellite comms and do the vast majority of both the processing and control from the ground. Or even data fusion from all the other airborne sensors - and perhaps reflections from ground emitters to build a multi-polar passive picture.

Etudiant, it's not that simple. Some of the manufacturing processes and alloys used 70 years ago have been effectively banned due to EPA and OSHA regulations. Newer processes and alloys result in parts that have different mass characteristics - which affects other parts in the engine - which in turn affect other parts, and pretty soon you need to remake the entire engine. So what you end up with is an very expensive re-development of a 70 year old engine design. All the costs of a new, modern engine with the crappy performance of the original.

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That seems just implausible to me. I don't know of an engine parts process that has been outlawed and I'm unaware of an relevant alloy that has become unavailable due to EPA and/or OSHA regs. We're not talking beryllium here, just simple nickel alloys, at least afaik. Happy to be corrected, but thus far I remain convinced it is just a case of too much money chasing limited spending opportunities.

That seems just implausible to me. I don't know of an engine parts process that has been outlawed and I'm unaware of an relevant alloy that has become unavailable due to EPA and/or OSHA regs. We're not talking beryllium here, just simple nickel alloys, at least afaik. Happy to be corrected, but thus far I remain convinced it is just a case of too much money chasing limited spending opportunities.

You can remain the skeptic, but I've seen it. For example, around 1990, GE ran into a big problem with voids in the turbine blades for their new engines - and many of the suspect parts had made it into service before the problem was discovered. Long story, but what they finally discovered was that - due to EPA regulations - the formulation for the stuff they used for the blade molds had changed. The new formulation eliminated a 'trace contaminant' which, it turns out, wasn't really a contaminant - it had acted to prevent the voids from forming in the blades. It costs GE million$ to develop a new process that didn't result in voids, and million$ more in inspections and warrantee costs. This on an engine that had been certified barely two years prior. GE also traced part of the problem with uncontained turbine disc failures on the CF6 engine to 'aftermarket' PMA turbine blades (Parts Manufacturing Authority) - the PMA blades were slightly heavier that the OEM blades which increased the stresses on the turbine disc. Sure, you can re-engineer and re-analyze everything that isn't exactly the same as it was 70 years ago (which would be pretty much the whole engine), but that takes a lot of time, and a lot of money. You're talking components spinning very rapidly, the failure of which can be catastrophic to the aircraft and crew. There is no such thing as a 'simple' change...